2. The 2001 NHS collected information about the health status of Australians, their use of health services and facilities and health-related aspects of their lifestyle. Previous surveys in the series were conducted in 1989-90 and 1995. Surveys conducted by the ABS in 1977-78 and 1983, while not part of the NHS series, also collected information similar to that obtained in the 2001 NHS.

3. Long-term health conditions are defined as those that have lasted or are expected to last for 6 months or more. Long-term health conditions are key indicators of the health status of the population and are a major factor in the usage of health services. Population-based information on the types and prevalence of long-term conditions is essential for the effective planning and provision of services and programs. The NHS meets these data needs by providing information on the:

Prevalence of long-term conditions in the population overall and in particular socio-demographic groups;

Relationships between relative health states/behaviours and the socio-demographic characteristics of the population; and

Changes in the prevalence and distribution of long-term conditions over time.

4. Crucial to the correct use and interpretation of time-series data from the NHS is an understanding of inter-survey comparability of the surveys. While the 2001 NHS is the same or similar in many ways to the 1995 NHS (and in part to the 1989-90 NHS), there are important differences across aspects of the surveys; sample design and coverage, survey methodology and content, definitions, classification, etc. These differences may affect the degree to which data are directly comparable between the surveys, and hence the interpretation of apparent changes over the period from 1989-90 to 2001. This document is intended as a guide to the reliability of the time-series for selected topics based on the questionnaire and classification methodology. For detailed information on other methodological aspects including sample design and coverage etc, see the 2001 NHS Users' Guide (pp155-169).

2.1 NHS redevelopment

5. The NHS is now planned to be conducted every three years. Changes to the 2001 NHS design from that used previously better meet the needs of key users, while maximising the reliability and validity of the data within cost and operational constraints.

6. The Commonwealth, State and Territory Governments have endorsed the National Health Priority Area (NHPA) initiative to focus attention and policy on the conditions which contribute most to the burden of illness in Australia, and have potential to respond to policy. These are:

Cardiovascular disease;

Cancer;

Injury prevention and control;

Mental health;

Diabetes; and

Arthritis and musculoskeletal conditions.

7. Given the policy importance of the NHPAs, the 2001 NHS questionnaire underwent significant revisions to provide more detailed information on several of the NHPAs. For the 2001 NHS, a new coding system to enable more accurate and consistent coding of reported conditions was also adopted. As a result of these changes, the quality of the benchmark estimates of many conditions is thought to have improved from the 1995 NHS. However, the degree of comparability has been affected somewhat for several of these and other long-term conditions. Other topic areas such as risk factors and health service use are largely unaffected by the changes to the NHS, and provide a stable time-series.